Beidou satellite can&;t see the roof of your house. Beidou system is used for positioning, navigation, time service, elevation measurement, as well as the unique function of sending short messages (GPS does not have this function). It receives signals from multiple satellites in the sky through a positioning receiver (such as a receiver in a car navigator), and then calculates your position coordinates. So it can&;t see the roof of your house. What satellite can see the information on the ground? China&;s high-scoring satellites can clearly see the ground information. Objects on the ground (such as the roof of your house) radiate and reflect electromagnetic waves. After receiving the signals, high-resolution satellites record them (just like cameras record the information of things on film) and then send them back to the ground receiving station. After correction and processing, satellite images are formed. The Google Maps we saw before is the product of such satellites. The positioning accuracy of Beidou system is divided into military and civilian categories, which is the same as GPS in the United States. The military accuracy of Beidou system is less than one meter, which is no different from that of the United States. The civilian accuracy reaches 5 meters, which is higher than that of the United States.